City have conceded 16 goals in eight games in all competitions since the start of the campaign and Maicon, set to return from injury against Fulham on Saturday, admits that Mancini is determined to address the situation.
"I know that Roberto is very focused on this." Maicon said. "He wants to improve and we have to improve quickly because we can't afford to have any more distance between us and the teams at the top of the league.
"The manager doesn't like conceding goals and he's very passionate about that and he's already working on it.
"We will do even more work and our focus is on improving that and improving the team's results as soon as possible.
"For me, it's difficult to say why (goals are being conceded) because I have just arrived, but the beginning of the season is difficult and a lot of clubs concede.
"But there is a minimum requirement that is always there and the players know they have to perform at that level."